One of the problems with sweeping statements like "life is precious" and "life is worth living" is that it presupposes that there is a universal fact called "life". We do, admittedly, use the term "life" in biology in a broad sense, such as "life began to evolve on land", and so on. But a site such as this one we are not talking about life in the general, biological sense. We are talking to individuals who are each living an individual life, and those lives can vary from other lives in a million ways. When you get right down to it, "life" in the singular really means little more than not being dead. A young soccer star who has just scored the winning goal in the finals and a 90-year-old dying of a painful disease are both deemed to be alive. Nature, or God, if you believe in God, has very little regard for life. Take one small example. There is a type of fly that reproduces by laying its eggs inside a certain type of caterpillar. The eggs hatch and the fly larvae grow strong and healthy by eating the poor caterpillar from the inside. The caterpillar finally dies after what is presumably a hell of suffering. Does the existence of such an arrangement imply any sort of caring god to you? When I say I would like to have the courage to do myself in, and people tell me "life" is precious, I feel like saying "On what do you base yourself to judge that MY life is precious? What information do you have about MY life (in the singular) to make that statement?" I am willing to admit that "life" in the generic sense is precious, but then again I am not proposing to wipe all living things off the planet, am I?